I'm imaging three laptops right now, and I need to record the actual hard drive size for our records. The listed size of two of the HDs is 150GB, so I'm assuming the actual size is 160GB. I have a third that is 160GB, so do I assume the actual size is 180GB? I asked around and was told that 180GB is a strange size for a HD, and also that it would be strange for the HD to actually be 200GB (20% of a HD being used for the FAT table seemed too much to the person I asked). Does anyone know what size I should record the 160 HD as, or maybe where I could find accurate information about the actual size of the HD? Thanks in advance for any help!
I'm imaging three laptops right now, and I need to record the actual hard drive size for our records. The listed size of two of the HDs is 150GB, so I'm assuming the actual size is 160GB.
Think of this way how to you test that assumption? Or, if I call it a 'hypothesis', does that ring any bells?
Hard disk manufacturers are a rare breed in that they almost invariably stick to the SI prefix system. To them, Giga means Giga, not Giga-and-a-bit-more.
Why not look for the product sheets or product user guides for the hard drives on the manufacturer's web site – they usually explain what is what.
You can get the listed HDD size from the label on the drive, and you can get the actual drive size from acquiring the physical drive (ie, FTK Imager and other tools will provide this in a text file along with the image).
Always get the LBA from the label. If you can't find it on the label then get it by researching it on the internet. Older drives might only list this as a CHS value and you'll have to work it out (C x H x S). Multiply the LBA or CHS result by the sector size and voila, you have your disk size.
Match the LBA (or CHS) to the sector count reported by your imaging tool and be on the lookout for an HPA or DCO.
Check out the sector size too as this can cause some imagers and other forensic software to barf when it isn't 512 bytes. It will affect your calculations as well.
Paul
Excellent, thanks for all of the help!